1. Field of the Invention
This invention relates to a forming apparatus for forming a web from stock. More particularly, this invention relates to a forming apparatus for forming a web of paper in the forming section of a papermaking machine.
2. Information Disclosure Statement
For many years, paper webs were formed by depositing a jet of pulp, or stock, onto a moving fourdrinier wire. Excess water within the deposited stock was drained through the fourdrinier wire by various dewatering means including suction boxes.
Paper webs formed as a result of the foregoing fourdrinier forming process resulted in a finished paper product exhibiting a certain two-sidedness in that the water, during formation, had been drained in one direction only. Such two-sidedness presented a finished sheet having different surface characteristics on each side of the sheet thereby causing printing problems.
More recently, various twin wire formers have been proposed which have enabled the dewatering of web in both directions simultaneously. Such twin wire formers have greatly increased the quality of the resultant paper product by providing a web having fairly uniform surface characteristics on both sides thereof.
However, many twin wire formers are disposed as retrofits above an existing fourdeinier forming section. In such retrofitted machines, the jet from the headbox is deposited on the moving fourdrinier wire and usually travels a considerable distance prior to entering the forming section defined by the cooperating bottom and top wire. During the movement of the wire prior to movement between the cooperating bottom and top wires, the web is subjected only to bottom drainage. Such bottom drainage has resulted in certain inherent characteristics of the resultant paper web and these characteristics have, to a large degree, been undesirable.
More specifically, during drainage of the web on the open wire between the headbox and the top wire when forming paper for newsprint, relatively high linting has resulted therefrom due to such bottom drainage. Furthermore, certain speed limitations have been imposed by the aforementioned open wire section and, to a degree, fines within the paper stock are unevenly distributed throughout the resultant web.
Additionally, in such twin wire formers, it is difficult to apply a gradual dewatering action to the stock so that the resultant web maintains therein, most of the fines that were suspended in the stock.
These, and other problems, are overcome by the apparatus of the present invention.
Consequently, it is primary objective of the present invention to provide a forming apparatus that overcomes the aforementioned inadequacies of the prior art machines and to provide a forming apparatus which contributes a significant improvement to the art of paper formation.
Another objective of the present invention is the provision of a forming apparatus in which the stock is subjected simultaneously to a gradual increase in dewatering action between the first and second ends of the forming section.
Another objective of the present invention is the provision of a forming apparatus in which the jet of stock is ejected directly into the forming section defined between a first and a second forming wire.
Another objective of the present invention is the provision of a forming apparatus in which the jet of stock is directed slightly towards the lower forming wire.
Another objective of the present invention is the provision of a forming apparatus including a first and second cooperating wire with a suction shoe disposed below the first wire and adjacent to the first end of the forming section for dewatering the web downwardly.
Another objective of the present invention is the provision of a dewatering shoe having a large radius of curvature such that a first portion of water is removed through the first wire and a second portion of water is removed upwardly through the second wire.
Another objective of the present invention is the provision of a forming apparatus including a suction slot for removing the second portion of water.
Another objective of the present invention is the provision of a suction roll disposed below the first wire with the roll having a radius of curvature which is less than the radius of curvature of the suction shoe such that a third portion of water is removed from the stock through the second wire.
Another objective of the present invention is the provision of a forming apparatus in which the roll is a grooved roll.
Another objective of the present invention is the provision of a forming apparatus in which the roll is disposed above the second wire such that the third portion of water is removed through the first wire.
Other objects and advantages of the present invention will be readily apparent to those skilled in the art by considering the information contained in the annexed drawings and the detailed description and as defined by the appended claims.